This invention relates to the field of immunogenic compositions which comprise an adjuvant. More particularly, the invention relates to adjuvanted immunogenic compositions (e.g., vaccines) against at least one or more Chlamydia species.
Chlamydial bacteria are obligate intracellular pathogens of eukaryotic cells. Three species of the family Chlamydia infect humans—C. trachomatis, C. pneumoniae, and C. psittaci—and genomic sequences for each of these are publicly available.
C. trachomatis organisms are dimorphic, and alternate between two distinct morphological forms, the infectious elementary bodies (EB) and the metabolically active reticulate bodies (RB). The EBs infect eukaryotic cells; they are endocytosed by mucosal cells into vesicular inclusions and are transformed into RB. Within the inclusion, the RBs replicate and redifferentiate into EBs before being released through cell lysis to infect neighbouring cells.
Chlamydia trachomatis is the most prevalent sexually transmitted bacterial pathogen in the world, with an estimated 100 million clinically diagnosed cases occurring annually. In addition, a similar or greater number of asymptomatic cases go undetected. The most common clinical presentations are urethritis and cervicitis. These acute manifestations typically resolve over a period of a few weeks. However, in certain patients, long-term sequelae may develop, including pelvic inflammatory disease, ectopic pregnancy, and infertility. In areas of the world with poor hygienic conditions, Chlamydia trachomatis causes trachoma and lymphogranuloma venerum (LGV). Although effective antibiotic therapy is available, eradication of these organisms will most likely only be achieved through a vaccination program. To date, no vaccine is commercially available against this infection.
Compositions including the major outer membrane protein (referenced herein as “MOMP”) of Chlamydia trachomatis are known. In particular, the article entitled, “Vaccination with the Chlamydia trachomatis Major Outer Membrane Protein Can Elicit an Immune Response as Protective as That Resulting from Inoculation with Live Bacteria”, Sukumar Pal et. al., Infection and Immunity, December 2005, p. 8153-8160 discloses the use of Chlamydia antigens in conjunction with adjuvants in an immunization composition. The publication discloses studies using the adjuvants CpG+alum, or CpG+Montanide ISA 720. According to the authors of this publication, the results obtained with these adjuvants were quite encouraging, but still required improvement. Moreover, while these adjuvants are quite suitable for animals, their ability to be used in humans is uncertain. Indeed, CpG oligonucleotides have been known to perform well in animals, but not so well in humans and Montanide ISA 720, a water-in-oil emulsion, can be rather painful when administered to humans.
Therefore, there still remains a need for a safe and effective immunogenic composition against Chlamydial infections.